Discovery of 14NH3 (2,2) maser emission in Sgr B2-Main

TL;DR

This paper reports the first detection of 14NH3 (2,2) maser emission in Sgr B2 Main, revealing unique maser spots with broad linewidths that challenge existing ammonia maser theories.

Contribution

It presents the discovery of the first 14NH3 (2,2) maser in Sgr B2 Main, with detailed high-resolution observations and analysis of its properties and uniqueness.

Findings

First 14NH3 (2,2) maser detected in Sgr B2 Main.

Maser spots are spatially unresolved but have broad linewidths.

No other ammonia lines are masers, challenging existing theories.

Abstract

We report the discovery of the first 14NH3 (2,2) maser, seen in the Sgr B2 Main star forming region near the center of the Milky Way, using data from the Very Large Array radio telescope. The maser is seen in both lower resolution (3" or ~0.1 pc) data from 2012 and higher resolution (0''.1 or ~1000 AU) data from 2018. In the higher resolution data ammonia (2,2) maser emission is detected toward 5 independent spots. The maser spots are not spatially or kinematically coincident with any other masers in this region, or with the peaks of the radio continuum emission from the numerous ultracompact and hypercompact \hii\, regions in this area. While the (2,2) maser spots are spatially unresolved in our highest resolution observations, they have unusually broad linewidths of several kilometers per second, which suggests that each of these spots consists of multiple masers tracing unresolved velocity structure. No other ammonia lines observed in Sgr B2 Main are seen to be masers, which continues to challenge theories of ammonia, maser emission that predict simultaneous maser emission in multiple ammonia transitions.